To increase mechanical strength, a gas-diffusion electrode substrate in a fuel cell conventionally uses a porous electrode substrate, which is a sheet-type carbon-carbon composite made by forming short carbon fibers into a sheet, binding the fibers to each other with an organic polymer and then sintering at high temperatures to carbonize the organic polymer (see patent publication 1).
Also, a porous electrode substrate, formed by forming a sheet from short oxidized fibers and sintering the sheet at high temperatures to carbonize the short oxidized fibers, is proposed to reduce costs (see patent publication 2).
Moreover, a porous electrode substrate, formed by making a sheet using short carbon fibers and acrylic pulp and sintering the sheet at high temperatures to carbonize the acrylic pulp, is proposed to reduce costs (see patent publication 3).